Laser processing, properties, and theoretical modeling of cobalt disilicide/silicon, titanium nitride/silicon, silicon/titanium nitride/silicon, and copper/titanium nitride/silicon heterostructures.

摘要

This dissertation describes experimental results and a theoretical model on the growth and characterization of thin film heterostructures useful for fabrication of advanced semiconductor devices. The dissertation combines novel materials processing with advanced materials characterization and modeling, and it involves a new mechanism of thin film growth, coined as domain epitaxy. A pulsed laser physical vapor deposition technique was employed to fabricate CoSi{dollar}sb2{dollar}/Si, TiN/Si, Si/TiN/Si, and Cu/TiN/Si heterostructures. Impetus for choosing these materials systems stemmed from the need of low resistivity ohmic contacts and interconnections which are stable at high operating temperatures, and the need for higher packing density in advanced ultra large scale integrated circuits.; For room temperature deposited CoSi{dollar}sb2{dollar} samples, the crystal structure is amorphous which is transformed to single crystal CoSi{dollar}sb2{dollar} after annealing at 650{dollar}spcirc{dollar}C for 20 minutes with a sheet resistance of 8 {dollar}Omega{dollar}/{dollar}square{dollar}. At a substrate temperature of 600{dollar}spcirc{dollar}C, the CoSi{dollar}sb2{dollar} is epitaxial on (100) Si substrate with a cube-on-cube orientation relation and a sheet resistance of 4 {dollar}Omega{dollar}/{dollar}square{dollar}. For TiN/Si heterostructure, the epitaxial growth of smooth TiN film was obtained at a substrate temperature of 600{dollar}spcirc{dollar}C and at a pulse energy density of 6-8 joules.cm{dollar}sp{lcub}-2{rcub}{dollar}. The TiN/Si(100) heterostructure has a resistivity of 15 {dollar}muOmega{dollar}-cm with a cube-on-cube orientation relation with the substrate. For Cu/TiN/Si heterostructures, the growth mechanism of copper films on TiN is strongly dependent on the pulse rate and the substrate temperature. At a pulse rate of 15 Hz, copper grows three-dimensionally on TiN with the island sizes ranging from 0.3-1.5{dollar}mu{dollar}m depending upon the substrate temperatures. At 30 Hz, copper grows uniformly on TiN with no detectable channels or holes and with a cube-on-cube orientation of the films with the substrate. The epitaxial Si/TiN/Si heterostructure was grown at a substrate temperature of 600{dollar}spcirc{dollar}C with a cube-on-cube epitaxial orientation relation.; CoSi{dollar}sb2{dollar} and Si have small lattice mismatch (misfit {dollar}sim{dollar}1.2%). Such small mismatch allows lattice matching to be favored because the coherency strains are small. The epitaxial growth in large lattice mismatch systems e.g. TiN/Si (misfit {dollar}sim{dollar}24.6%), Cu/TiN (misfit {dollar}sim{dollar}15.8%), and Si/TiN (misfit {dollar}sim{dollar}24.6%) were obtained by domain epitaxial growth. In these cases, there are 4-to-3 match in unit cells for TiN/Si structure and 7-to-6 match for Cu/TiN structure giving rise to remaining lattice misfits of only 4.0 and 0.6% respectively. A theoretical modeling was performed for Si/TiN/Si heterostructures to demonstrate that domain epitaxy is, in fact, the energetically favorable mechanism for epitaxial growth of these two films on the Si substrate.